Americans sit more than ever before – at work, at school, even at play. Chained to your chair? Well, obesity expert Dr. James Levine calls that dangerous behavior. Like tobacco, he says, sitting is hazardous to your health.

“Sitting all day long is literally killing us,” claims Levine who treats obesity at the Mayo Clinic, one of the country's premiere research hospitals.

Levine’s research has turned conventional thinking about exercise on its head. Many think a dose of exercise is a perfect prescription for good health, but Levine’s research shows that a daily trip to the gym, while beneficial, can’t undo the damage done from sitting all day.

“A few years ago, I would have actually said to you, you know, the person who's doing that session at the gym once a day is doing everything they need to do. But the data that are now coming up suggests that's not the case, “Levine told NBC News’ Natalie Morales in an interview airing Thursday, Jan. 10 on NBC’s Rock Center with Brian Williams. “Being sedentary for nine hours a day at the office is bad for your health whether you go home and watch television afterwards or hit the gym. It is bad whether you are morbidly obese or marathon-runner thin. It appears that what is critical and maybe even more important than going to the gym, is breaking up that sitting time.”

The way Dr. Levine describes it, sitting isn't pretty. The body’s metabolic engines go to sleep. The muscles stop moving all together and the heart slows. Then, the body's calorie-burning rate plummets to about one calorie per minute -- a third of what it would be if you were walking. Insulin effectiveness drops and the risk of developing Type 2 diabetes rises. Fat and cholesterol levels rise too.

“It is almost like sort of owning a really cool sports car and letting it idle all day long. The engine gets gunked up. That's what happens to our bodies. The body, as we know, simply isn't built to sit all day,” Levine said.

Levine figured this out in 1999 when he asked a simple question: if two people eat the same thing and do not exercise, why does one gain weight and not the other? To do his experiment, Levine needed to devise a way to get an accurate measurement. He designed special tracking gear with sensors attached. The read out became his EKG of how much a person moves and with how much exertion.

Once he interpreted his data, Levine made a key discovery in understanding obesity. How much a person moves is a big dividing line between who’s obese and who’s not.

“People who are lean, even who don't go to the gym, move about two and a quarter hours a day more than people with obesity, “ Levine learned. “Somehow those individuals are finding the opportunities to walk to the trashcan, to walk down to accounting, to go to the bathroom, or the coffee shop, whatever it may be. “

And people who fidget are actually in better shape than people who don’t.

“It's sort of the brain's signal to move. When you see somebody who's naturally fidgety, those fidgets are probably the propellants for them to get up and move,” said Levine of fidgeting.

While Levine says there is unquestionably “ a very significant genetic component” to obesity and that nutrition is very important, he also says: “We all live in the same society. We all have desks and chairs and sofas and Lazy Boy armchairs and TVs. We all have the same stuff. We all live in the same environment, but half of us have a weight problem and half of us don't. “

The shifts from rural life to the city life, the car and computer revolutions, have all conspired to make us walk less and sit more, Levine argues.

”All of the sudden if you take that historical view of this, you realize we're living a completely different way to how we were designed. I mean it is inconceivable that we were ever going to be a group, a population, a species sitting on our bottoms all day long. We're just not meant to do that. So is it a surprise that the consequences are devastating? No,” Levine said.

Levine has some common sense solutions for people interested in improving their health by spending less time at their desks. Take a walk with a friend at lunchtime, have a walking meeting with a colleague, go the restroom that is farther away from your desk.

Ten years ago , Levine came up with the ultimate way to move more at work. He invented the treadmill desk. At first, he says, people thought he was crazy.

“When I first came up with idea, I was thought to be a complete lunatic. People were writing me, like, notes, and it was like… ‘Jim, you must be joking. Like are you out of your mind,’” he said

Levine consulted with a company to get the desk made, but receives no profit from its sales. So far, nearly 60,000 units have been sold.

But if there’s no treadmill desk in your future Levine has a simple solution: Get up for 10 minutes every hour.